THE SKULL. 45 
presphenoid, and each half of it is produced caudad near the 
middle line into a triangular spine which lies ventrad of the 
body of the presphenoid. The horizontal portion of the bone 
helps to separate the olfactory and respiratory passages of the 
nasal chamber, while its vertical portion contributes to the 
formation of the nasal septum. 
The ventral margin formed by the junction of the two 
halves of the bone is smooth and free caudad, but at its cranial 
end is broad and rough for articulation with the palatal 
processes of the maxille. 
Palatine Bone. Os palatinum (Fig. 33).—The palate 
bone or palatine bone consists of two portions, a horizontal or 
palatal portion (2) and a perpendicular or nasal portion (6), 
uniting at an angle of about forty-five degrees. 
The horizontal portions (a) of the two bones are received 
between the maxillary bones and form the caudal and medial 
part of the roof of the mouth. Each is irregularly 
quadrilateral in form, with the caudolateral angle 
produced caudad into a long process which is 
continuous with the perpendicular portion of the 
bone. The lateral margin of the horizontal por- 
tion articulates over its cranial half with the 
maxillary bone. At about its middle a short thick % 
maxillary spine (c) projects caudolaterad. The Fic. 33.—Para- 
remainder of the lateral margin is directly con- Rie sane) 
tinuous with the perpendicular plate of the bone. a, __ horizontal 
The medial margin is rough for articulation with Portion; 4 per- 
: pendicular _por- 
the corresponding margin of the opposite pala- tion; ¢, maxillary 
tine; the caudal angle of this margin Projects aL ee 
caudad as the short posterior nasal spine (@). sphenopalatine 
: . Jick foramen; /, cau. 
The caudal margin forms a free edge which g,) opening of 
bounds the choane; it passes laterally into the Ce palatine 
canal. 
perpendicular portion. 
The ventral surface (Fig. 41, 8) looks into the mouth. 
Near the middle of its craniolateral margin are two or more 
small foramina (Fig. 41, g) which form the cranial temination 
of the posterior palatine canal. The dorsal surface is smooth 
and looks into the nasal cavity. 
